1. Field of the Invention
The present invention relates to a liquid discharging method, a liquid jet head, and a liquid jet apparatus for discharging a desired liquid by the creation of air bubbles brought about by causing thermal energy to act upon liquid. More particularly, the invention relates to a liquid discharging method, a liquid jet head, and a liquid jet apparatus provided with a movable member to be displaced by the utilization of the air bubble creation.
The present invention is also applicable to a printer for recording on a recording medium, such as paper, thread, fabric, cloth, leather, plastic, glass, wood, or ceramics, and to a copying machine, a facsimile equipment provided with communication systems, a word processor and other apparatuses having a printing unit therefor. Further, the present invention is applicable to a recording system for industrial use, which is complexly combined with various processing apparatuses.
Here, the term xe2x80x9crecordingxe2x80x9d in the description of the present invention means not only the provision of images having characters, graphics, or other meaningful representation, but only the provision of those images that do not present any particular meaning, such as patterns.
2. Related Background Art
There has been known the so-called bubble jet recording method, which is an ink jet recording method whereby to form images on a recording medium by discharging ink from discharge ports using acting force exerted by the change of states of ink brought about by the abrupt voluminal changes (creation of air bubbles) when thermal energy or the like is applied to ink in accordance with recording signals. For the recording apparatus that uses the bubble jet recording method, it is generally practiced to provide, as disclosed in the specifications of U.S. Pat. No. 4,723,129 and others, the discharge ports that discharge ink, the ink paths conductively connected to the discharge ports, and electrothermal transducing elements arranged in each of the ink paths as means for generating energy for discharging ink.
In accordance with such recording method, it is possible to record high quality images at high speeds with a lesser amount of noises. At the same time, the head that executes this recording method makes it possible to arrange the discharge ports for discharging ink in high density, with the excellent advantage, among many others, that images are made recordable in high resolution, and that color images are easily obtainable by use of a smaller apparatus. In recent years, therefore, the bubble jet recording method is widely adopted for many kinds of office equipment, such as a printer, a copying machine, a facsimile equipment. Further, this recording method is utilized even for industrial systems, such as a textile printing, among others.
Along the wider utilization of bubble jet technologies and techniques for various products in many different fields, there have been increasingly more demands in recent years as given below.
For example, as to the demand on the improvement of energy efficiency, the adjustment of the thickness of protection film has been studied to optimize the performance of heat generating elements. A study of the kind has produced effects on the enhancement of transfer efficiency of generated heat to liquids.
Also, in order to obtain high quality images, there has been proposed a driving condition under which a liquid discharging method or the like is arranged to be able to execute good ink discharges at higher ink discharging speeds with more stabilized creation of air bubbles. Also, from the viewpoint of a high-speed recording, there has been proposed the improved configuration of liquid flow paths that makes it possible to obtain a liquid jet head capable of refilling liquid to the liquid flow paths at higher speeds in order to make up the liquid that has been discharged.
Of the various configurations of liquid flow paths thus proposed, the structure of liquid flow paths and a method for manufacturing heads, which are disclosed in the specification of Japanese Patent Application Laid-open No. 63-199972, are the inventions devised with attention given to the back waves (the pressure directed opposite to the direction toward the discharge ports, that is, pressure exerted in the direction toward the liquid chamber). The back waves are known as energy loss because such energy is not exerted in the discharging direction.
However, with respect to the structure as disclosed, it is clearly understandable that the partial suppression of the back waves is not practical for liquid discharge when studies are made on the condition under which the air bubbles are created in the liquid flow path that retains the discharging liquid in it.
Fundamentally, the back waves themselves are not related directly with discharging as described above. Of the pressures exerted by the air bubble, those directly related with discharging have already acted upon liquid so that the liquid is in the state of being discharged from the liquid flow path the moment the back waves are generated in the flow path. Therefore, even if the back waves are suppressed, it is clear that no significant influence is exerted on the liquid discharge, not to mention the partial suppression as described earlier.
On the other hand, for the bubble jet recording method, each of the heat generating elements repeats heating, while being in contact with ink. As a result, deposit is accumulated on the surface of each heat generating element due to burning of ink. Depending on the kinds of ink, such deposit is made in a considerable quantity, and results in the instabilized creation of air bubbles, hence making it difficult to perform ink discharges in good condition. Also, it is desired to provide a method for performing discharges in good condition without changing the quality of discharging liquid even when the liquid used has the nature such as to be easily deteriorated by the heat application or such as to make sufficient bubbling difficult.
Here, with this in view, there has been proposed a method for discharging liquid by transferring pressure exerted by bubbling to discharging liquid, while arranging means for separating the liquid used to create air bubbles by the application of head (bubbling liquid) and the liquid for use of discharges (discharging liquid) as different liquids, such as disclosed in the specifications of Japanese Patent Application Laid-Open No. 61-69467, Japanese Patent Application Laid-Open No. 55-81172, U.S. Pat. No. 4,480,259, among some others. In accordance with these disclosures, the structure is arranged to completely separate ink serving as discharging liquid, and bubbling liquid by use of silicon rubber or some other flexible film so as not to allow the discharging liquid to be directly in contact with the heat generating elements, and at the same time, to transfer pressure exerted by bubbling of the bubbling liquid to the discharging liquid by means of the deformation of the flexible film. With a structure of the kind, it is attained to prevent the deposit from being accumulated on the surface of each heat generating element, the improvement of selection range of discharging liquids, or the like.
However, the structure that completely separates discharging liquid and bubbling liquid as described above is the one whereby to transfer pressure exerted at the time of bubbling to discharging liquid by means of the deformation of the flexible film brought about by its expansion and contraction. Therefore, the pressure exerted by the deforming thereof is absorbed by the flexible film to a considerable extent. Also, the amount of deformation of the flexible film is not large. As a result, although it is possible to obtain effect that discharging liquid and bubbling liquid are made separable, there is a fear that energy efficiency and discharging power are lowered after all.
The applicant hereof has filed an application for a patent of such an extremely high technical standard as compared with the conventional technical level that the developing component of each air bubble on the downstream side is positively transferred to the free end side of each movable member with a view to enhancing the conventionally fundamental discharging characteristics of the liquid discharging method that form air bubbles (particularly, the air bubbles following film boiling) basically in each of the liquid flow path to such a high standard that has been expected in the conventional art. The invention has been designed with the thought that the development component of the air bubble on the downstream side should be taken into account for a remarkable enhancement of the discharging characteristics in consideration of the behavior of energy given to the discharge amount by the air bubbles themselves, and that the development component of each air bubble should be made changeable in the discharging direction effectively.
The present invention is an invention based on a new knowledge for the provision of a new discharging method and discharging principle, which make it possible to improve the discharging principle and the functional effects of the epoch-making previous invention still more.
In other words, the new knowledge means the acquirement of a technique that makes it possible to improve the displacement environment still more by the phenomenal analysis with respect to the free end of each movable member before its displacement begins, and then, to implement further development or induction of each air bubble and the transfer of liquid, which are synthetically formed, toward the discharge port side, including the formation of structure, which is capable of effectively utilizing the power obtainable from each of the air bubble generating areas as a desired objective.
The present invention is designed by giving attention to the physical state of the relationship between the movable members and the air bubbles, which includes inventions with respect to the new discharging principle, structural features, and many other aspects.
The major objectives of the invention is given below. It is a first object thereof to provide an extremely new liquid discharging principle by means of a fundamental control of the created air bubbles.
It is a second object of the invention to provide a liquid discharging method, a liquid jet head, and others capable of discharging liquid in excellent condition by improving the pressure distribution in liquid to be exerted at the time of bubbling for the further enhancement of discharging efficiency, and by improving the displacement environment of the free end of each movable member for directing each of the air bubbles toward each of the discharge ports.
It is a third object of the invention to provide a liquid discharging method, a liquid jet head, and others capable of enhancing the printing speed or the like by suppressing the action of the inertial force caused by the back waves in the direction opposite to the direction of liquid supply, and at the same time, by reducing the regressive amount of meniscus by use of the valve mechanism of each of the movable member for the enhancement of refilling frequency.
In order to achieve the objects described above, the present invention relates to a liquid discharging method comprising the step of displacing the free end of each movable member following the creation of each air bubble in the air bubble generating area,
the fulcrum of the movable member being positioned on the side different from liquid discharging side with respect to the displacement area for the free end of the movable member to be displaceable, at the same time, the free end thereof being arranged to face the effective bubbling area positioned on the downstream side of the central portion of the length of the effective bubbling area forming the air bubble generating area in the direction of the movable member from the fulcrum to the free end thereof, and a part of the effective bubbling area positioned to face the free end thereof on the downstream side of the effective bubbling area being arranged to face the displacement area directly.
Also, the part of the effective bubbling area facing the displacement area directly is arranged to include the most downstream side with respect to the effective bubbling area in the aforesaid direction.
Also, the part of the effective bubbling area facing the displacement area directly is a range of 5 xcexcm or more as the range with respect to the aforesaid direction.
Also, the inclination of pressure in the vicinity of the displacement area of the free end of the movable member is intensified by means of a structure for reflecting or inducing the acoustic waves generated at the time of bubbling in the effective bubbling area.
Also, the air bubbles are created by means of film boiling phenomenon in the effective bubbling area of each heat generating elements.
Also, the present invention relates to a liquid jet head for displacing the movable member, each having the free end, together with air bubble created in the air bubble generating area by means of each of the electrothermal transducing elements,
the fulcrum of the movable member being positioned on the side different from liquid discharging side with respect to the displacement area for the free end of the movable member to be displaceable, at the same time, the free end thereof being arranged to face the effective bubbling area positioned on the downstream side of the central portion of the length of the effective bubbling area forming the air bubble generating area in the direction of the movable member from the fulcrum to the free end thereof, and a part of the effective bubbling area positioned to face the free end thereof on the downstream side of the effective bubbling area being arranged to face the displacement area directly.
Also, the part of the effective bubbling area facing the displacement area directly is arranged to include the most downstream side with respect to the effective bubbling area in the aforesaid direction.
Also, the part of the effective bubbling area facing the displacement area directly is a range of 5 xcexcm or more as the range with respect to the aforesaid direction.
Also, the inclination of pressure in the vicinity of the displacement area of the free end of the movable member is intensified by means of a structure for reflecting or inducing the acoustic waves generated at the time of bubbling in the effective bubbling area.
Also, the air bubbles are created by means of film boiling phenomenon in the effective bubbling area of each heat generating elements.
Also, the present invention relates to a liquid jet apparatus using the aforesaid liquid jet head, which is provided with a structure capable of supplying equal liquid to the displacement area and the air bubble generating area.
Also, a liquid jet head using the aforesaid liquid jet head comprising:
a first structure for supplying a first liquid to the displacement area; and
a second structure for supplying a second liquid different from the first liquid to the air bubble generating area in a state of the second liquid being separated from the first liquid.
Also, a liquid jet head using the aforesaid liquid jet head comprises:
means for carrying a recording medium to the printing area to provide liquid discharged from the head therefor; and
driving means for providing driving condition for the electrothermal transducing elements of the head.
In this respect, the term xe2x80x9creplacement area of the free end of the movable memberxe2x80x9d is a concept that includes the area in the vicinity of the liquid path area that presents the locus when the free end is displaced. The term xe2x80x9ceffective area of the air bubblexe2x80x9d means the area of each electrothermal transducing area where each air bubble is essentially created excluding such surface where bubbling is not generating at the initial stage.
Under condition that the free end is positioned on the discharge port side than the fulcrum of the movable member, the present invention makes it possible to utilize the environment that facilitates the movement of the free end of each movable member for the formation of pressure inclination that enables the movement of the free end directly with respect to the directly inducing portion of the air bubble created in the effective bubbling area to the discharge port, which is placed on the front portion on the downstream side of the central part in the direction from the fulcrum to the free end of the movable member. In other words, the acoustic waves (compressional waves) generated in the effective bubbling area at the time of air bubble creation are propagated directly in liquid to form the pressure inclination (distribution) in the liquid on the displacement area reliably at the initial stage with respect to the displacement area (liquid flow path). As a result, it becomes possible to increase the shifting amount toward the discharge port in the liquid residing in the moving direction of the movable member on the free end and in the vicinity of the free end of the movable member.
Also, in accordance with the present invention, it is possible to shift the liquid dividing area that disperses the flow of liquid to the fulcrum side of the surface area of the movable member in each of the displacement areas, thus stabilizing the discharge amount of liquid still more. This arrangement results in the enhancement of the discharging efficiency, and in the rationalized refilling function when liquid is refilled, thus leading to a shorter refilling period.
Also, in accordance with the reflection of the acoustic waves or the structure of induction itself of the present invention, the aforesaid pressure inclination (distribution) can be intensified independently. Therefore, it is possible to move liquid as desired. With this reflection or the inductive structure provided in addition to the effective bubbling area that directly faces the displacement area in accordance with the present invention, the formation of the aforesaid environment becomes more reliable and presents excellent effect. Also, by the utilization of this structure, it becomes possible to implement the induction of the air bubbles to the discharge port side more rationally to enhance the overall of discharging effect of an invention to be described later, which will be added to the first invention in the claim 1 as has been discussed above.
The advantages and features of the inventions hereof and the examples of structural variation will be clear to those skilled in the art by reference to the specific description given below.
In this respect, the terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d are related with the direction of liquid flow from the supply source of liquid to the discharge port through the air bubble generating area (or the movable member) or these terms are often used to express the structural direction thereof.
Also, the term xe2x80x9cdownstream sidexe2x80x9d of the air bubble itself represents the portion of the air bubble on the discharge port side, which mainly acts upon the discharge droplets directly. More specifically, it means the downstream side with respect to the center of the air bubble in the flow direction or the structural direction described above or the air bubble created in the area on the downstream side of the center of area of the heat generating element.
Also, the term xe2x80x9cessentially closedxe2x80x9d used in the description of the present invention means a state where the air bubble does not escape from the gap (slit) on the circumference of the movable member before the movable member is displaced at the time of the air bubble being created.
Further, the term xe2x80x9cseparation wallxe2x80x9d referred to in the present invention means a wall (that may include the movable member) that resides to partition the air bubble generating area and the discharge port in a broader way, and also, means the partition between the flow path including the air bubble generating area and the liquid flow path conductively connected with the discharge port directly, in a narrower way, so as to prevent liquid in each of the areas from being mixed.
Furthermore, the term xe2x80x9cessentially in contactxe2x80x9d referred to the present invention includes a state where at least a part of the air bubble and the movable member are in contact physically, and a state where the development of the air bubble or the movement of the movable member is regulated, although a slight liquid film is present between the air bubble and the movable member.